1. Field of the Invention
The present invention relates to a method of recording information on an optical record medium such as an optical card.
2. Description of the Related Art
There have been proposed various types of optical cards. FIG. 1 shows one of known optical cards. On the optical card 1, a plurality of tracks 53 are provided in parallel with each other, and information is recorded and reproduced at a unit of track. The information is recorded and reproduced optically as a change in the optical reflectance. On the optical card 1, there are further provided ID (identification) regions 52a, 52b and 52c, in which a predetermined pattern for identifying a track and a track number are pre-recorded. The optical card 1 illustrated in FIG. 1 can be inserted into a card recording and/or reproducing apparatus in opposite directions, so that ID regions are provided not only at both ends of the tracks, but also at centers of the tracks. The track 53 further includes data regions 51a and 51b in which data has been recorded or will be recorded. That is to say, the optical card 1 is of the once-write type.
FIG. 2 is a schematic view depicting a detailed track format in an area A shown in FIG. 1. Each of the tracks 53 has a width corresponding to a sum of widths of twenty one lines, and sixteen lines are formed in a track 53 which are separated from each other equidistantly in a direction perpendicular to a track direction in which the tracks extend. Hereinafter, this direction perpendicular to the track direction is called a seek direction, because a light spot is moved in this direction during a seek operation for finding a desired track. Sixteen lines in a track are divided into two groups each of which includes eight lines. Between these two groups there is formed a guide line region 54 consisting of a series of rectangles arranged regularly.
Each of data regions 51a and 51b is divided into blocks 58 viewed in the track direction, each of which constitutes a unit block of data. Between successive blocks 58 as well as between the ID regions 52a, 52b and end blocks 58, there are formed frame identification patterns 59. During the seek operation, the optical card 1 and an optical head are moved in the seek direction relative to each other and track numbers 56-1 to 56-8 and identification patterns 57-1 to 57-8 in the ID region 52a or 52b are read out. During the reproduction, sixteen data bits in a data region 51a are simultaneously read out, so that the reproduction can be performed at a very high speed.
In Japanese Patent Application Laid-open Publication Kokai Hei 2-12672, there is proposed a known method of recording information on the above explained optical card. In this known method, an error correction is carried out in accordance with the (272, 190) majority logic decodable cycle code, and the data is recorded on the optical card 1 such that data bits are distributed among a track. In the present specification, this interleave is called an in-track interleave.
Successive steps of the known information recording method will be explained with reference to schematic views shown in FIGS. 3A to 3E.
(1) A information code (user data) is divided into 208 blocks (BL) each having 23 bytes (B) as shown in FIG. 3A.
(2) Error correction codes are added to the information code to form a code length data (packet P) having 272 bytes (34B) to form 208 packets as depicted in FIG. 3B.
(3) Corresponding bytes (1B to 34B) in each packets P are collected as shown in FIG. 3C.
(4) Each packet is divided into lower significant four bits (X L) and higher significant four bits (X H), X=1, 2, 3 (FIG. 3D).
(5) The lower and higher significant four bits are interleaved for respective frames over a whole track 53 and frame identification patterns 59 are formed between successive frames 58 as illustrated in FIG. 3E.
In this manner, all the packets 1P to 208P are interleaved among a whole track, so that the reproduction can be performed reliably. That is to say, when a part of the data recorded on the optical card 1 could not be read out correctly due to injuries, damages or stains, the original user data can be correctly reproduced.
In the known information recording method explained above, a writing laser beam emitted from a semiconductor laser has to be positioned onto successive lines in a track each time respective bits are recorded. That is to say, at first the laser beam is positioned onto a first line in the track and a least significant bit of a first byte 1B in a first packet 1P is recorded, and then the laser beam is jumped onto a second line in the relevant track and a next least significant bit of the first byte 1B in the first packet 1P is recorded, and so on. After a fourth bit counted from the least significant bit of a first byte 1B in a fourth packet 4P has been recorded on a sixteenth line, the laser beam moves onto the first line and at the same time the optical card is moved in the track direction by one bit pitch. Then, a least significant bit of a first byte 1B in a fifth packet 5P is recorded on the first line. It should be noted that the positioning of the laser beam onto respective lines requires a given time period, so that the recording time becomes very long.
Further, in the known information recording method, although an amount of data to be recorded in a single track is small, the data is interleaved in the whole track, so that the recording time could not be shortened at all. In this case, dummy bits, e.g. zero bits are allocated to vacant portions in 208 packets. In practice, important data such as card managing data is recorded in a duplicated manner. That is to say, the same managing data is recorded on two different tracks which are separated from each other by a relatively large distance. Usually the card managing data has a small data length, so that the efficiency of usage of the optical card is decreased, because the card managing data is also interleaved in the whole track.